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Design of the pulse duty cycle of the pseudolite signal in local area augmentation systems

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Science China(Physics,Mechanics & Astronomy) 2011年第6期54卷 1004-1008页

作者： LI ChunXia CHEN JinPing CHU HengLin beijing global information application and development center Beijing 100094China

The short-pulse TDMA signal is an excellent solution to the near-far problem in the pseudolite augmentation systems,and the pulse duty cycle is an important element in the *** paper aims at designing the duty cycle of the pseudolite pulse signals with a theoretical *** first,the scope of the duty cycle is derived theoretically with the object of ensuring the reception of both the pseudolite signals and the satellite signals,and the expression for the theoretical upper limit is *** based on the proposed expression,the duty cycles of Galileo pseudolite pulse signals are *** theoretical upper limit can guide the design of the short-pulse TDMA pseudolite signals.

关键词： pseudolite short-pulse TDMA duty cycle

Recent Advances in Artificial Sensory Neurons:Biological Fundamentals,Devices,applications,and Challenges

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Nano-Micro Letters 2025年第3期17卷 168-216页

作者： Shuai Zhong Lirou Su Mingkun Xu Desmond Loke Bin Yu Yishu Zhang Rong Zhao Guangdong Institute of Intelligence Science and Technology HengqinZhuhai 519031People’s Republic of China College of Integrated Circuits Zhejiang UniversityHangzhou 3112000People’s Republic of China ZJU-Hangzhou global Scientific and Technological Innovation center Hangzhou 310027People’s Republic of China Department of Science Mathematics and TechnologySingapore University of Technology and DesignSingapore 487372Singapore Department of Precision Instruments Tsinghua UniversityBeijing 100084People’s Republic of China center for Brain‑Inspired Computing Research Tsinghua UniversityBeijing 100084People’s Republic of China IDG/McGovern Institute for Brain Research Tsinghua UniversityBeijing 100084People’s Republic of China

Spike-based neural networks,which use spikes or action potentialsto represent information,have gained a lot of attention because of their high energyefficiency and low power *** fully leverage its advantages,convertingthe external analog signals to spikes is an essential *** including analog-to-digital converters or ring oscillators,and sensorssuffer from high power and area *** efforts are devoted to constructingartificial sensory neurons based on emerging devices inspired by the biologicalsensory *** can simultaneously perform sensing and spike conversion,overcoming the deficiencies of traditional sensory *** review summarizesand benchmarks the recent progress of artificial sensory *** starts with thepresentation of various mechanisms of biological signal transduction,followed bythe systematic introduction of the emerging devices employed for artificial ***,the implementations with different perceptual capabilitiesare briefly outlined and the key metrics and potential applications are also ***,we highlight the challenges and perspectives for the future development of artificial sensory neurons.

关键词： Artificial intelligence Emerging devices Artificial sensory neurons Spiking neural networks Neuromorphic sensing

Performance evaluation method of hybrid navigation constellations with invalid satellites

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Science China(Physics,Mechanics & Astronomy) 2011年第6期54卷 1046-1050页

作者： YANG Yang PENG Bo DONG XuRong FAN Li LIU Li WANG Wei Academy of Equipment Command & Technology Beijing 101416China beijing global information center of application and Exploitation Beijing 100094China

The construction of a navigation system plays an important role in the development of national politics,economy and military ***,the Beidou navigation system is facing a transition period from the regional navigation system to the global *** the global constellation,the system performance will not be seriously degraded when one or two satellites are invalid,but it is out of case for the regional constellation,which usually has fewer satellites and less *** paper deals with this problem of hybrid constellations and analyzes the influence of the disabled satellites on the *** hybrid constellations and simulation methods designed,the influence of invalid satellites on the navigation system is fully investigated.

关键词： hybrid constellation regional navigation satellite invalidation performance evaluation

Multipath error detection and correction for GEO/IGSO satellites

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Science China(Physics,Mechanics & Astronomy) 2012年第7期55卷 1297-1306页

作者： WU XiaoLi ZHOU JianHua WANG Gang HU XiaoGong CAO YueLing Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030China beijing global information application and development center Beijing 100094China

Constellations of regional satellite navigation systems are usually constituted of geostationary satellites (GEO) and inclined geostationary satellites (IGSO) for better service availability. Analysis of real data shows that the pseudorange measurements of these two types of satellites contain significant multipath errors and code noise, and the multipath for GEO is extremely serious, which is harmful to system services. In contrast, multipath error of carrier phase measurements is less than 3 cm, which is smaller than the multipath of pseudorange measurements by two orders of magnitude. Using a particular combination of pseudorange and dual-frequency carrier phase measurements, the pseudorange multipath errors are detected, and their time varying features are analyzed. A real-time multipath correction algorithm is proposed in this paper, which is called CNMC (Code Noise and Multipath Correction). The algorithm decreases the influence of the multipath error and therefore ensures the performance of the system. Data processing experiments show that the multipath error level may be reduced from 0.5 m to 0.15 m by using this algorithm, and 60% of GEO multipath errors and 42% of IGSO multipath errors are successfully corrected with CNMC. Positioning experiments are performed with a constellation of 3 GEO plus 3 IGSO satellites. For dual-frequency users the East-West position accuracy is improved from 1.31 m to 0.94 m by using the CNMC algorithm, the South-North position accuracy is improved from 2.62 m to 2.29 m, and the vertical position accuracy is improved from 4.25 m to 3.05 m. After correcting multipath errors, the three-dimensional position accuracy is improved from 5.16 m to 3.94 m.

关键词： multipath error carrier smoothing pseudorange GEO satellite position error

Orbit determination and time synchronization for a GEO/IGSO satellite navigation constellation with regional tracking network

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Science China(Physics,Mechanics & Astronomy) 2011年第6期54卷 1089-1097页

作者： ZHOU ShanShi HU XiaoGong WU Bin LIU Li QU WeiJing GUO Rui HE Feng CAO YueLing Wu XiaoLi ZHU LingFeng SHI Xin TAN HongLi Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China Graduate University of Chinese Academy of Sciences Beijing 100049China beijing global information application and development center Beijing 100094China

Aiming at regional services,the space segment of COMPASS (Phase I) satellite navigation system is a constellation of Geostationary Earth Orbit (GEO),Inclined Geostationary Earth Orbit (IGSO) and Medium Earth Orbit (MEO) *** orbit determination (POD) for the satellites is limited by the geographic distribution of regional tracking *** time synchronization (TS) system is developed to supplement the regional tracking network,and satellite clock errors and orbit data may be obtained by simultaneously processing both tracking data and TS ***,inconsistency between tracking system and TS system caused by remaining instrumental errors not calibrated may decrease navigation *** the other hand,POD for the mixed constellation of GEO/IGSO/MEO with the regional tracking network leads to parameter estimations that are highly *** example of correlation is found between GEO's orbital elements and its clock *** estimate orbital elements and clock errors for a 3GEO+2IGSO constellation in this study using a multi-satellite precise orbit determination (MPOD) strategy,with which clock error elimination algorithm is applied to separate orbital and clock estimates to improve numerical *** Laser Ranging (SLR) data are used to evaluate User Ranging Error (URE),which is the orbital error projected on a receiver's line-of-sight ***-way radio-wave time transfer measurements are used to evaluate clock *** with data from the regional tracking network,we conclude that the fitting of code data is better than 1 m in terms of Root-Mean-Square (RMS),and fitting of carrier phase is better than 1 *** orbital evaluation,difference between computed receiver-satellite ranging based on estimated orbits and SLR measurements is better than 1 m (RMS).For clock estimates evaluation,2-hour linear-fitting shows that the satellite clock rates are about 1.E-10 s/s,while receiver clock rates a

关键词： POD time synchronization clock errors elimination SLR evaluation

Positioning accuracy assessment for the 4GEO/5IGSO/2MEO constellation of COMPASS

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Science China(Physics,Mechanics & Astronomy) 2012年第12期55卷 2290-2299页

作者： ZHOU ShanShi CAO YueLing ZHOU JianHua HU XiaoGong TANG ChengPan LIU Li GUO Rui HE Feng CHEN JunPing WU Bin Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China beijing global lnformation application and development center Beijing 100094China

Determined to become a new member of the well-established GNSS family,COMPASS(or BeiDou-2) is developing its capabilities to provide high accuracy positioning *** positioning modes are investigated in this study to assess the positioning accuracy of COMPASS' 4GEO/5IGSO/2MEO *** Point Positioning(PPP) for geodetic users and real-time positioning for common navigation users are *** evaluate PPP accuracy,coordinate time series repeatability and discrepancies with GPS' precise positioning are *** show that COMPASS PPP repeatability for the east,north and up components of a receiver within China's Mainland is better than 2 cm,2 cm and 5 cm,*** systematic offsets of several centimeters exist between COMPASS precise positioning and GPS precise positioning,indicating errors remaining in the treatments of COMPASS measurement and dynamic models and reference frame differences existing between two *** common positioning users,COMPASS provides both open and authorized services with rapid differential corrections and integrity information available to authorized *** assessment shows that in open service positioning accuracy of dual-frequency and single-frequency users is about 5 m and 6 m(RMS),respectively,which may be improved to about 3 m and 4 m(RMS) with the addition of differential *** accurate Signal In Space User Ranging Error(SIS URE) and Geometric Dilution of Precision(GDOP) contribute to the relatively inferior accuracy of COMPASS as compared to *** the deployment of the remaining 1 GEO and 2 MEO is not able to significantly improve GDOP,the performance gap could only be overcome either by the use of differential corrections or improvement of the SIS URE,or both.

关键词： PPP real-time positioning authorized services orbit determination

Improvement of orbit determination for geostationary satellites with VLBI tracking

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Chinese Science Bulletin 2011年第26期56卷 2765-2772页

作者： HUANG Yong HU XiaoGong ZHANG XiuZhong JIANG DongRong GUO Rui WANG Hong SHI ShanBin Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China beijing global information application and development center Beijing 100094 China beijing Institute of Tracking and Telecommunications Technology Beijing 100094 China

China’s COMPASS satellite navigation system consists of five or more geostationary (GEO) *** roles of GEO satellites are to improve the regional user’s positioning accuracy and provide the continuous Radio Determination Satellite *** motion of GEO satellites relative to a ground tracking station is almost fixed,and regular orbit maneuvers are necessary to maintain the satellites’ allocated positions above the *** features present difficulties in precise orbit determination (POD).C-band ranging via onboard transponders and the L-band pseudo-ranging technique have been used in the COMPASS *** paper introduces VLBI tracking,which has been successfully employed in the Chinese lunar exploration programs Chang’E-1 and Chang’E-2,to the POD of GEO *** contrast to ranging,which measures distances between a GEO satellite and an observer,VLBI is an angular measurement technique that constrains the satellite’s position errors perpendicular to the satellite-to-observer *** a demonstration,the Chinese VLBI Network organized a tracking and orbit-determination experiment for a GEO navigation satellite lasting 24 *** paper uses the VLBI delay and delay-rate data,in combination with C-band ranging data,to determine the GEO satellite’s *** accuracies of the VLBI delay and delay rate data are about 3.6 ns and 0.4 ps/s,*** analysis shows that the VLBI data are able to calibrate systematic errors of the C-band ranging data,and the combination of the two observations improves orbit prediction accuracy with short-arc data,which is important for orbital recovery after maneuvers of GEO *** the implementation of VLBI2010,it is possible for VLBI to be applied in the COMPASS satellite navigation system.

关键词：地球静止卫星地面跟踪站 VLBI 轨道测定北斗卫星导航系统位置误差定位精度测量技术

Precise orbit determination for geostationary satellites with multiple tracking techniques

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Chinese Science Bulletin 2010年第8期55卷 687-692页

作者： GUO Rui HU XiaoGong TANG Bo HUANG Yong LIU Li CHENG LiuCheng HE Feng Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China Graduate University of Chinese Academy of Sciences Beijing 100039 China beijing global information application and development center Beijing 100094 China

A new precise orbit determination (POD) strategy based on the combination of satellite laser ranging (SLR) and C-band transfer ranging for geostationary satellites (GEO) is *** approaches to calibrate ranging biases of the C-band ranging system are proposed,namely the two tracking system co-location comparison and the combined POD method,with calibration accuracies estimated to be 0.5 ns and 1 ns *** data from a C-band tracking network in China,POD experiments indicate that meter-level POD accuracy is achievable for ***-mean-square (RMS) of the post-fit C-band ranging data is about 0.205 *** radial component errors of POD are evaluated with SLR data from a station in beijing,with residual RMS of 0.133 *** overlapping experiments show the total orbit error is a few *** of SLR residuals also suggest that for 2-hour prediction,the predicted radial error is about 0.373 m.

关键词：地球静止卫星卫星轨道确定跟踪系统过氧化物酶技术校准精度地球同步轨道激光测距

Research on Autonomous Orbit Determination of Navigation Satellite Based on Crosslink Range and Orientation Parameters Constraining

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Geo-Spatial information Science 2006年第1期9卷 18-23页

作者： CAI Zhiwu ZHAO Dongming CHEN Jinping JIAO Wenhai center of information application and development Around World P. O. Box 5136 Beijing 100094 China

Autonomous navigation of navigation satellite is discussed. The method of auto-orbit determination using the erosslink range and orientation parameters constraining is put forward. On the basis of the analysis of its ... 详细信息

关键词： satellite navigations autonomous navigations orbit determination